The present invention relates generally to the field of compositions, kits, and methods for inducing an immune response against a disease. In particular, the invention relates to compositions, kits, and methods for administering a relatively low dose of antigen for inducing an immune response against a disease as compared to conventional compositions, kits, and methods.
T-helper (Th) lymphocytes may be categorized into two distinct subsets of effector cells based on their functional capabilities and cytokine profiles. Th1 cells produce IFN-γ, TNF-β, and IL-2 and help to activate macrophages and cytotoxic T lymphocytes. In addition, Th1 cells assist other immune cells in the production of those antibody isotypes that promote opsonization. Th2 cells trigger B cells to produce and secrete antibodies. In contrast, Th2 cells are particularly effective at inducing B cells to produce certain antibody isotypes such as IgE and IgA, which neutralize intercellular pathogens and help opsonization, complement, mast cell, and eosinophil activation. Because of these functional differences, Th1 and Th2 exhibit different efficiency in elimination of a selected pathogen. Diseases that can be prevented or treated successfully by Th1 responses include mycobacterial infections such as tuberculosis, leprosy, leishmaniasis, and schistosomiasis, which are intracellular infections, and certain viral diseases. Th2 responses are protective against helminths and some bacteria such as pneumo- and meningococcii.
Th1 and Th2 cells arise from a common precursor cell called Th0. Differentiation of T-helper cells into Th1 and Th2 cells is an important event in determining the outcome of an immune response (i.e., whether a pathogen will persist, whether the host will be protected, and/or whether the host will experience immunopathogenesis). Infectious pathogens may exhibit a predisposition to induce a cell-mediated form of immunity versus a humoral form of immunity. Successful defense against intracellular pathogens tends to be associated with Th1 dominance and resultant cellular cytolytic activity, whereas resistance to extracellular infectious pathogens is most often dominated by Th2 effectors, which lead to the production of high levels of antigen-specific immunoglobulins. Therefore, a better understanding of the factors that contribute to differentiation of Th0 cells into Th1 and Th2 cells will help facilitate preparation of more effective prevention and treatment strategies.